Support frame for an embolic protection device

ABSTRACT

An embolic protection device comprises a collapsible filter element for delivery through a vascular system of a patient. The filter element comprising a collapsible filter body and a filter support frame contacting the filter body. The collapsible filter body has an inlet end and an outlet end, the inlet end of the filter body having one or more inlet openings sized to allow blood and embolic material to enter the filter body, the outlet end of the filter body having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter body. The filter support frame is movable between a collapsed position for movement through the vascular system and an extended outwardly projecting position to support the filter body in the expanded position. The frame has a plurality of engagement segments which are spaced-apart longitudinally and transversely when the filter body is in the deployed expanded configuration to urge the filter body into opposition with the vessel wall. The engagement segments define at least partially a substantially helical engagement track.

This application is a continuation of U.S. application Ser. No.11/505,469 filed Aug. 17, 2006, which is a continuation of U.S.application Ser. No. 10/797,612 filed Mar. 11, 2004, now abandoned,which is a continuation of U.S. application Ser. No. 09/986,132 filedNov. 7, 2001, now abandoned, which is a continuation of PCT/IE00/00054,filed May 8, 2000, and claims benefit under 35 U.S.C. § 119 toInternational Application No. PCT/IE99/00035 filed on May 7, 1999, allof the disclosures of which are hereby incorporated by reference intheir entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a filter element for a transcatheter embolicprotection device.

2. Description of the Related Art

The invention is particularly concerned with filter elements fortranscatheter embolic protection devices of the type described in ourWO-A-9923976. One type of such embolic filter essentially comprises afilter body mounted on an associated collapsible support frame which canbe collapsed by means of a catheter for deployment of the filter througha patient's vascular system. Upon retraction of the catheter the supportframe and filter body expand outwardly from across a blood vessel withinwhich the filter is positioned to filter blood flowing through the bloodvessel.

The support structure is generally of superelastic or shaped memorymaterial such as Nitinol™ which provides the circumferential pressure onexpansion to secure the filter body in a close fit within the vessel.

It is important to achieve apposition of a filter body with the wall ofthe vessel in which the filter is deployed to ensure that there is nopathway between the filter body and the vessel wall through whichembolic material could pass. This is not a simple issue in view of thewide variations in vessel geometry and the variable physical propertiesof a vessel lining at different locations even within a singlevasculature.

When the filter element is being pulled through a small diameter conduitor opening for loading and retrieval, there are certain forces exertedon the support frame. The first is on entry of the proximal end into thetube and when the whole of the proximal end has been inserted into thetube and the distal end is about to be inserted into the catheter tube.Considerable loading forces are generated which in some cases requireconsiderable retraction forces to overcome.

There is therefore a need to provide a support frame for a filter whichwill address these problems.

SUMMARY OF THE INVENTION

According to the invention there is provided an embolic protectiondevice comprising:

-   -   a collapsible filter element for delivery through a vascular        system of a patient;    -   the filter element comprising a collapsible filter body and a        filter support frame contacting the filter body;    -   the collapsible filter body having an inlet end and an outlet        end, the inlet end of the filter body having one or more inlet        openings sized to allow blood and embolic material to enter the        filter body, the outlet end of the filter body having a        plurality of outlet openings sized to allow through passage of        blood but to retain undesired embolic material within the filter        body;    -   the filter support frame having a longitudinal axis and being        movable between a collapsed position for movement through the        vascular system and an extended outwardly projecting position to        support the filter body in the expanded position;    -   the frame having a plurality of engagement segments, the        engagement segments being spaced-apart longitudinally and        transversely when the filter is in the deployed expanded        configuration to urge the filter body into apposition with the        vessel wall.

In one embodiment of the invention the engagement segments define atleast one at least partially substantially helical engagement track.

Preferably the frame comprises a number of frame elements, at least someof the frame elements having an engagement segment. Ideally at leastsome of the frame elements are interconnected.

In another embodiment of the invention the frame has an intermediatesection and a proximal section extending from the intermediate section,the engagement segments being provided in the intermediate section ofthe frame. Preferably the proximal section of the frame extends radiallyinwardly of the intermediate section and defines at least one inlet holeto accommodate inflow of embolic material to be captured in the filter.Most preferably the proximal section of the frame has a proximalmounting for mounting on a filter carrier. Ideally the proximal mountingis substantially tubular.

The proximal mounting may be offset with respect to the longitudinalaxis of the support frame.

In a particularly preferred embodiment, the proximal section of theframe is flexible with respect to the intermediate section of the frame.Ideally the proximal section of the frame comprises a number of proximalelements, at least some of which are of a flexible material. Mostpreferably the proximal section of the frame comprises a plurality offlexible elements of relatively low column strength which are movableindividually and independently of the intermediate section between tautand slack configuration.

In a further embodiment of the invention the frame includes a distalsection extending from the intermediate section, the distal section ofthe frame being flexible with respect to the intermediate section of theframe. Preferably the distal section of the frame includes a pluralityof flexible elements of relatively low column strength which are movableindividually and independently of the intermediate section between tautand slack configurations. Ideally the flexible elements are thread-likeelements. Most preferably at least some of the flexible elements definetethers.

In another preferred embodiment of the invention the frame has a distalsection extending from the intermediate section. Preferably the distalsection of the frame extends radially inwardly of the intermediatesection. Ideally the distal section of the frame has a distal mountingfor mounting on a filter carrier.

The distal mounting is preferably substantially tubular.

In one embodiment of the invention the distal mounting is offset withrespect to the longitudinal axis of the support frame.

Preferably the distal section of the frame is flexible with respect tothe intermediate section of the frame.

At least the intermediate section of the support frame may be formedfrom wire.

Alternatively at least the intermediate section of the support frame maybe formed by a slotted tube.

In a preferred embodiment at least the intermediate section of thesupport frame is an elastic, superelastic and/or a shaped memorymaterial. Ideally at least the intermediate section of the support frameis of Nitinol™.

Desirably the included angle defined between adjacent frame elements isless than 90°. Most preferably the included angle is less than 60°.

In a further preferred embodiment at least a portion of a support frameelement is offset from the longitudinal axis by an angle of less than45° in the expanded configuration.

Desirably a support frame element is offset from the longitudinal axisby an angle of less than 10° when the frame is in the collapsedconfiguration. Most preferably a support frame element is offset fromthe longitudinal axis by angles of less than 5° when the frame is in thecollapsed configuration.

Ideally the engagement segments are defined by segments of a singleframe element. The frame element is preferably at least partially ofhelical shape.

Desirably the collapsible filter body is mounted to the support frame.

In another aspect the invention provides an embolic protection devicecomprising:

-   -   a collapsible filter element for delivery through a vascular        system of a patient;    -   the filter element comprising a collapsible filter body and a        filter support frame contacting the filter body;    -   the collapsible filter body having an inlet end and an outlet        end, the inlet end of the filter body having one or more inlet        openings sized to allow blood and embolic material to enter the        filter body, the outlet end of the filter body having a        plurality of outlet openings sized to allow through passage of        blood but to retain undesired embolic material within the filter        body;    -   the filter support frame having a longitudinal axis and being        movable between a collapsed position for movement through the        vascular system and an extended outwardly projecting position to        support the filter body in the expanded position;    -   the frame having an intermediate section and a proximal section        extending from the intermediate section; and    -   the proximal section of the frame being flexible with respect to        the intermediate section of the frame.

In one embodiment of the invention the proximal section of the framecomprises a plurality of flexible elements of relatively low columnstrength which are movable individually and independently of theintermediate section between taut and slack configuration.

In a preferred embodiment the frame includes a distal section extendingfrom the intermediate section, the distal section of the frame beingflexible with respect to the intermediate section of the frame.Preferably the distal section of the frame includes a plurality offlexible elements of relatively low column strength which are movableindividually and independently of the intermediate section between tautand slack configurations. Ideally the flexible elements are thread-likeelements.

Most preferably at least some of the flexible elements define tethers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood by the followingdescription of some of the embodiments thereof, given by way of exampleonly, with reference to the accompanying drawings, in which:

FIG. 1 is a partially sectioned elevational view of an embolicprotection device;

FIG. 2 is a schematic sectional elevational view of the embolicprotection device of FIG. 1;

FIG. 3 is a detailed sectional view of a portion of the device of FIG.1;

FIG. 4 is a longitudinal cross-sectional view of the device of FIG. 1;

FIG. 5 is a cross-sectional view of a distal end of the device of FIG.1;

FIG. 6 is a view on the line A-A in FIG. 5;

FIG. 7 is a perspective view of a filter body of the device of FIGS. 1to 6;

FIG. 8 is a side elevational view of the filter body of FIG. 7;

FIG. 9 is a view of a proximal end of the filter body;

FIG. 10 is a perspective view of a support frame of the device of FIGS.1 to 6;

FIG. 11 is a side elevational view of the support frame;

FIG. 12 is a perspective view illustrating the manufacture of thesupport frame;

FIG. 13 is a view of the support frame and filter element assembly;

FIG. 14 is a longitudinal cross-sectional view of a filter elementaccording to the invention;

FIG. 15 is a longitudinal cross-sectional view of a support frame of thefilter element of FIG. 14;

FIG. 16 is a cross-sectional view on the line III-III of FIG. 15;

FIG. 17 is a cross-sectional view on the line IV-IV of FIG. 15;

FIG. 18 is a cross-sectional view on the line V-V of FIG. 15;

FIG. 19 is a longitudinal cross-sectional view of another support frame;

FIG. 20 is a side elevational view of a filter support frame accordingto another embodiment of the invention;

FIG. 21 is a side elevational view of another support frame of theinvention;

FIG. 21A is a side view of one support element of the frame of FIG. 21;

FIG. 22 is a perspective view of another support frame;

FIG. 23 is a longitudinal cross-sectional view of a further supportframe, in a deployed use configuration;

FIG. 24 is a side view of another support frame in a partially collapsedconfiguration;

FIG. 25 is a longitudinal cross-sectional view of the support frame ofFIG. 24 in a deployed use configuration;

FIG. 26 is a side view of another support frame;

FIG. 27 is a side view of a still further support frame and filter ofthe invention;

FIG. 28 is a perspective view of another support frame;

FIG. 29 is a perspective view of yet another support frame;

FIGS. 30 and 31 are side views of another support frame in differentpositions of use;

FIGS. 32 and 33 are perspective views of a support frame in differentpositions of use;

FIG. 34 is a perspective view of a further support frame of theinvention; and

FIG. 35 is a perspective view of the support frame of FIG. 34 and anassociated filter.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 to 13 there is illustrated an embolic protectiondevice as described in our WO-A-9923976 indicated generally by thereference number 100. The device 100 has a guidewire 101 with a proximalend 102 and a distal end 103.

A tubular sleeve 104 is slidably mounted on the guidewire 101. Acollapsible filter 105 is mounted on the sleeve 104, the filter 105being movable between a collapsed stored position against the sleeve 104and an expanded position as shown in the drawings extended outwardly ofthe sleeve 104 for deployment in a blood vessel.

The sleeve 104 is slidable on the guidewire 101 between a pair ofspaced-apart end stops, namely an inner stop 106 and an outer stop whichin this case is formed by a spring tip 107 at the distal end 103 of theguidewire 101.

The filter 105 comprises a filter body 110 mounted over a collapsiblesupport frame 111. The filter body 110 is mounted to the sleeve 104 ateach end, the body 110 being rigidly attached to a proximal end 112 ofthe sleeve 104 and the body 110 being attached to a collar 115 which isslidable along a distal end 114 of the sleeve 104. Thus the distal endof the body 110 is longitudinally slidable along the sleeve 104. Thesupport frame 111 is also fixed at the proximal end 112 of the sleeve104. A distal end 116 of the support frame 111 is not attached to thesleeve 104 and is thus also free to move longitudinally along the sleeve104 to facilitate collapsing the support frame 111 against the sleeve104. The support frame 111 is such that it is naturally expanded asshown in the drawings and can be collapsed inwardly against the sleeve104 for loading in a catheter 118 or the like.

The filter body 105 has large proximal inlet openings 117 and smalldistal outlet openings 119. The proximal inlet openings 117 allow bloodand embolic material to enter the filter body, however, the distaloutlet openings 119 allow through passage of blood but retain undesiredembolic material within the filter body.

An olive guide 120 is mounted at a distal end of the sleeve 104 and hasa cylindrical central portion 121 with tapered ends 122, 123. The distalend 122 may be an arrowhead configuration for smooth transition betweenthe catheter and olive surfaces. The support frame 111 is shaped toprovide a circumferential groove 125 in the filter body 110. If thefilter is too large for a vessel, the body may crease and this groove125 ensures any crease does not propagate along the filter.

Enlarged openings are provided at a proximal end of the filter body 110to allow ingress of blood and embolic material into an interior of thebody 110.

In use, the filter 105 is mounted in a collapsed state within a distalend of the catheter 118 and delivered to a deployment site. When thefilter is correctly positioned the catheter 118 is retracted allowingthe support frame 111 to expand expanding the filter body 110 across thevessel in which the filter is mounted. Blood and emboli can enter theenlarged openings at a proximal end of the filter body 110. The bloodwill pass through the filter wall, however, the openings or pores in thefilter are sized so as to retain the embolic material. After use thecatheter is delivered along the guidewire 101 and slid over the filter105 engaging the proximal inlet end 112 first to close the openings andthen gradually collapsing the filter body against the sleeve 104 as thecatheter 118 advances over the filter 105. Once the filter 105 is fullyloaded in the catheter 118, it can then be withdrawn.

It will be noted that a proximal end of the filter is fixed and a distalend of the filter is longitudinally movable along the sleeve tofacilitate collapsing of the filter body.

Further, the catheter engages the proximal end of the filter body firstthus closing the filter body inlet and preventing escape of embolicmaterial from the filter body as the filter body is being collapsed.

The outer filter body 110 is preferably of a resilient biocompatibleelastomeric material. The material may be a polyurethane based material.There are a series of commercially available polyurethane materials thatmay be suitable. These are typically based on polyether or polycarbonateor silicone macroglycols together with diisocyanate and a diol ordiamine or alkanolamine or water chain extender. Examples of these aredescribed in EP-A-461,375 and U.S. Pat. No. 5,621,065. In addition,polyurethane elastomers manufactured from polycarbonate polyols asdescribed in U.S. Pat. No. 5,254,622 (Szycher) are also suitable.

The filter material may also be a biostable polycarbonate urethanearticle an example of which may be prepared by reaction of anisocyanate, a chain extender and a polycarbonate copolymer polyol ofalkyl carbonates. This material is described in our WO-A-9924084. Thefilter material may be manufactured from a block and cut into a desiredshape. However the filter is preferably formed by dipping a rod ofdesired geometry into a solution of the material which coats the rod.The rod is then dissolved. The final geometry of the filter may bedetermined in the dipping step or the final geometry may be achieved ina finishing operation. Typically the finishing operations involveprocesses such as mechanical machining operations, laser machining orchemical machining.

The filter body is of hollow construction and is formed as describedabove by dipping a rod in a solution of polymeric material to coat therod. The rod is then dissolved, leaving a hollow body polymericmaterial. The rod may be of an acrylic material which is dissolved by asuitable solvent such as acetone.

The polymeric body thus formed is machined to the shape illustrated inFIGS. 1 to 13. The final machined filter body comprises an inlet orproximal portion 210 with a proximal neck 212, and outlet or distalportion 213 with a distal neck 214, and an intermediate portion 215between the proximal and distal portions.

The inlet holes 117 are provided in the proximal portion 210 which allowthe blood and embolic material to flow into the filter body. In thiscase the proximal portion 210 is of generally conical shape to maximizethe hole size.

The intermediate portion 215 is also hollow and in this case is ofgenerally cylindrical construction. This is important in ensuring morethan simple point contact with the surrounding blood vessel. Thecylindrical structure allows the filter body to come into soft contactwith the blood vessel to avoid damaging the vessel wall.

The intermediate portion 215 is provided with a radial stiffening means,in this case in the form of a radial strengthening ring or rim 220. Thering 220 provides localized stiffening of the filter body withoutstiffening the material in contact with the vessel. Such an arrangementprovides appropriate structural strength so that line apposition of thefilter body to the vessel wall is achieved. It is expected that othergeometries of stiffening means will achieve a similar result.

The tubular intermediate portion 215 is also important in maintainingthe stability of the filter body in situ to retain captured emboli andto ensure that flow around the filter is minimized. For optimumstability we have found that the ratio of the axial length of theintermediate portion 215 of the filter body to the diameter of theintermediate portion 215 is preferably at least 0.5 and ideally greaterthan 1.0.

The collapsible support frame 111 has four foldable arms 290 which arecollapsed for deployment and upon release extend outwardly to expand thefilter body 110.

The support frame 111 can be manufactured from a range of metallic orpolymeric components such as a superelastic or shape memory alloy likeNitinol™ or a shape memory polymer or a shaped stainless steel or metalwith similar properties that will recover from the deformationsufficiently to cause the filter body 110 to open.

The support frame may be formed as illustrated in FIG. 12 by machiningslots in a tube 291 of superelastic material or shape memory alloy suchas Nitinol™. On machining, the unslotted distal end of the tube forms adistal collar 293 and the unslotted proximal end of the tube forms aproximal collar 294. In use, the distal collar 293 is slidably moveablealong the tubular sleeve 104 which in turn is slidably mounted on theguidewire 101 for deployment and retrieval. The proximal collar 294 isfixed relative to the tubular sleeve 104.

Alternatively, the construction may be made entirely of wiresinterconnected at various points.

To load the filter, the sub assembly of the support frame and filterbody is pulled back into the catheter 118 to engage the distal stop 107.The support arms 290 are hinged inwardly and the distal collar 293 movesforward along the tubular sleeve 104. As the support arms 290 enter thecatheter 118 the filter body 110 stretches as the filter body collar 115slides along the tubular sleeve 104 proximal to the olive 120. Ondeployment, the catheter 118 is retracted proximally along the guidewire101 initially bringing the collapsed filter assembly with it until itengages the proximal stop 106. The catheter sleeve then begins torelease the filter freeing the support arms 290 to expand and the filterbody apposes the vessel wall.

For retrieval, a retrieval catheter is introduced by sliding it over theguidewire 101 until it is positioned at the proximal end of the filterbody and support frame. Pulling the guidewire 101 will initially engagethe distal stop 107 with the filter element and begin to pull it intothe retrieval catheter. The initial travel into the delivery catheteracts to close the proximal openings of the filter element, thusentrapping the embolic load. As the filter continues to be pulled backthe filter body and the support frame are enveloped in the retrievalcatheter. The collapsed filter may then be removed from the patient.

Various support frames according to the invention are described belowwith reference to FIGS. 14 to 35. In each case the frame has a pluralityof engagement segments formed on one or more support arms (some of whichmay be interconnected). The engagement segments are spaced-apartlongitudinally and transversely when the filter is in the deployedexpanded configuration to urge the filter body into apposition with thevessel wall. The support frames of the invention provide apposition ofthe filter body to the wall of a vessel in which the filter is deployed.This is achieved while reducing the loading forces required to load thefilter into a delivery catheter for deployment and for loading thefilter into a retrieval catheter for retrieval of the filter togetherwith any embolic material captured by the filter.

Referring to FIGS. 14 to 18 there is illustrated a support frameindicated generally by the reference numeral 30 for a filter 31. Thefilter support frame 30 comprises a plurality of support elements eachof which extend in a longitudinal direction. Some of the supportelements provide support for one portion of the filter body 31 and someprovide support for another portion of the filter body 31. In this casethere are six support arms, three arms 30, 31, 22 providing support fora proximal end of the filter body 31 and three arms 23, 24, 25 providingsupport for a distal end of the filter body 31. The support arms 20, 21,22, 23, 24, 25 each have engagement sections to engage the filter body.The engagement segments are spaced-apart longitudinally and transverselywhen the filter is in the deployed expanded configuration. Apposition isthereby improved while loading forces are greatly reduced allowing thefilter to be more easily loaded and retrieved.

Referring to FIG. 19 there is illustrated another support frame 40similar to that of FIGS. 14 to 18. In this case adequate support isprovided while omitting the distal collar 293. This frame 40 is easilyformed and the same principle may be applied to other frames as thosedescribed above and below.

Referring to FIG. 20 there is illustrated another support frame 50 whichcomprises four support arms 51, 52, 53, 54. Each of the arms 51, 52, 53,54 is of at least partially helical shape and different engagementsegments 51 a, 52 a, 53 a, 54 a of the arms are spaced-apartlongitudinally and transversely when the filter is in the deployedexpanded configuration illustrated. This arrangement is especiallyadvantageous because it is relatively easily formed and providesexcellent apposition with reduced loading forces.

Referring to FIG. 21 there is illustrated another support frame 55according to the invention. The support frame 55 comprises six supportelements 56, one of which is shown in FIG. 21A. Each element 56 includesa distal or proximal tether section 57 and a closed loop portion 58extending from the tether section 57. The loops 58 have engagementsections 59 and the engagement sections of the frame are longitudinallyand transversely spaced-apart to achieve apposition in a central sectionof the frame 55.

Referring to FIG. 22 there is illustrated a further support frame 60comprising six separate support elements 61, 62, 63, 64, 65, 66 whichare again arranged to provide engagement segments 61 a, 62 a, 63 a, 64a, 65 a, 66 a which are longitudinally and transversely spaced-apart toprovide apposition while requiring reduced loading forces.

Referring to FIG. 23 another support frame 70 of the invention is madefrom twisted wires of a shaped memory/superelastic material such asNitinol™. In this there are four support elements, each provided by atwisted wire 71. The wires 71 are joined together by twisting atproximal and distal ends. The wires 71 are joined together in a centralregion between the distal and proximal ends to form a lattice-likestructure 72 which defines a plurality of longitudinally andtransversely spaced-apart engagement segments.

Referring to FIG. 24 there is illustrated a support frame 75 which is inthe form of a lattice-like arrangement to achieve substantial appositionto a vessel wall in use as illustrated in FIG. 25.

In FIG. 26 there is illustrated a support frame 76 similar to the frame75 of FIGS. 24 and 25. In this case the lattice in a central region isof generally hexagonal shape.

Referring to FIG. 27 there is illustrated a filter comprising a filtermembrane 78 supported by a support frame 79. The support frame 79comprises a distal lattice portion 79 a, a proximal lattice portion 79 band a series of interconnecting struts in a central portion 79 c. Inthis case the support frame 79 is attached by connections 80 to thefilter membrane 78. The filter support frame 79 is mounted to the filterbody and is independent of the guidewire. Therefore lateral movement ofthe guidewire will not affect the position of the filter support frameand apposition will not be adversely affected by guidewire movement.

Referring to FIG. 28 another support frame 82 according to the inventioncomprises a number of frame elements which divide intermediate theproximal and distal ends into loops 83 which define engagement segments.

In FIG. 29 there is illustrated another support frame 85 similar to theframe of FIG. 28 and like parts are assigned the same referencenumerals. In this case the frame elements 82 are not interconnected atthe distal end.

Referring now to FIGS. 30 and 31 there is illustrated another filtersupport frame 85 according to the invention which is similar to theembodiment of FIG. 21 described above and like parts are assigned thesame reference numerals. In this case the filter frame is proximallyconnected by means of two or more, preferably three flexible, (lowcolumn strength) threads/monofilaments 86. The threads 86 may be movedindividually and independently of the intermediate section between aslack and taut configuration. This allows for a greater freedom ofmovement of the guidewire relative to the center of the lumen withoutdistorting the filter element. This is particularly advantageous incurved vasculatures where the guidewire may have the tendency to moveaway from the centre of the lumen, or in embodiments such as offsetfilters where the delivery of interventional catheters proximal to thefilter may cause the guidewire to move towards the centre thus causingthe filter to distort.

Referring to FIGS. 32 and 33 there is illustrated an offset filter 90according to the invention. The frame may be of Nitinol™ wire of slottedtube configuration. One or more support elements 91 define a loop likestructure at an angle at the proximal end to define a proximal inlethole 92. The design for the intermediate and the distal sections of thefilter may vary. In the embodiment illustrated there are two supportelements 91 which form a partial helical structure along the peripheryof the filter membrane. The offset design allows for a single, largeproximal hole diameter, thus enabling the capture of large emboli andalso maximum space for blood flow within the filter. The guidewireenters the filter through a proximal collar off the center of thevasculature.

Referring to FIGS. 34 and 35 there is illustrated another offset filter95 according to the invention which is similar to the filter of FIGS. 32and 33. In this case there is a single support element 96. The membraneis self-supported at the distal end.

The support frame may comprise one or a number of support elementsextending in a substantially longitudinal direction. In a preferredembodiment, at least a portion of the longitudinal support element isoffset by less than 45° from its longitudinal axis. This providescircumferential apposition while greatly reducing the loading forces. Inits collapsed configuration, the support elements are preferably offsetwithin 10° preferably within 5° of the longitudinal axis.

It will be appreciated that the local stiffeners of the support elementcan be reduced in the collapsed state by having an undulating/curvedsection about which the collapsed filter can bend. This providesincreased flexibility during delivery in an arrangement such as that ofFIG. 20 described above.

The invention is not limited to the embodiments hereinbefore describedwhich may be varied in both construction and detail.

1. An embolic protection filter comprising: a filter body having aninlet end and an outlet end, the inlet end of the filter body having oneor more inlet openings sized to allow blood and embolic material enterthe filter body, the outlet end of the filter body having a plurality ofoutlet openings sized to allow through passage of blood but to retainundesired embolic material within the filter body; a support frame tosupport the filter body in an expanded position; a proximal couplingpart for coupling the filter to a guidewire; and a distal coupling partfor coupling the filter to a guidewire; the proximal coupling part beingseparate from and longitudinally spaced apart from the distal couplingpart; the support frame connecting the proximal coupling part to thedistal coupling part.
 2. A filter as claimed in claim 1, wherein thecoupling part defines a lumen therethrough through which a guidewire isinsertable.
 3. A filter as claimed in claim 2, wherein the coupling partis movable relative to the guidewire.
 4. A filter as claimed in claim 3,wherein the coupling part is rotatable relative to the guidewire.
 5. Afilter as claimed in claim 3, wherein the coupling part is movablelongitudinally relative to the guidewire.
 6. A filter as claimed inclaim 2, wherein the coupling part comprises a tube.
 7. A filter asclaimed in claim 1, wherein the support frame comprises one or moresupport arms extending from the proximal coupling part to the distalcoupling part.
 8. A filter as claimed in claim 7, wherein the supportarm is flexible.
 9. A filter as claimed in claim 8, wherein the supportarm has substantially zero column strength.
 10. A filter as claimed inclaim 8, wherein the support arm comprises a tether.
 11. A filter asclaimed in claim 7, wherein the support arm is rigid.
 12. A filter asclaimed in claim 11, wherein the support arm has substantial columnstrength.
 13. A filter as claimed in claim 11, wherein the support armis formed of a slotted tube.
 14. A filter as claimed in claim 7, whereinthe support arm extends longitudinally from the proximal coupling partto the distal coupling part.
 15. A filter as claimed in claim 7, whereinthe support arm extends at least partially circumferentially from theproximal coupling part to the distal coupling part.
 16. A filter asclaimed in claim 15, wherein the support arm extends at least partiallyhelically from the proximal coupling part to the distal coupling part.17. A filter as claimed in claim 7, wherein two or more of the supportarms are interconnected.
 18. A filter as claimed in claim 17, whereinthe support frame comprises a mesh of support arms.